Fluid migration shut-off

ABSTRACT

A downhole assembly, including a line operatively arranged to carry a first fluid, and a trap arranged in fluid communication with the line, the trap operatively arranged to enable the first fluid to flow in a first direction, while capturing a second fluid in a compartment, thereby preventing migration of the second fluid through the line in a second direction opposite to the first direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of an earlier filing date from U.S. Provisional Application Ser. No. 61/500,995 filed Jun. 24, 2011, the entire disclosure of which is incorporated herein by reference.

BACKGROUND

Chemical injection systems are used in the downhole drilling and completions industry. Check valves are included to prevent natural gas and other fluids from undesirably migrating up through the chemical injection lines. The performance of these check valves is not always adequate to prevent all fluid migration, particularly under static conditions (no chemical being injected) or while chemicals are being injected at lower rates. Problems with check valves may include debris caught in the valves, wear or degradation of the valves over time, problematic installations, etc. Accordingly, advances in preventing fluid migration are always well received by the industry.

BRIEF DESCRIPTION

A downhole assembly, including a line operatively arranged to carry a first fluid, and a trap arranged in fluid communication with the line, the trap operatively arranged to enable the first fluid to flow in a first direction, while capturing a second fluid in a compartment, thereby preventing migration of the second fluid through the line in a second direction opposite to the first direction.

A method of operating a downhole system, including injecting a first fluid through a line in a first direction and capturing a second fluid in a compartment connected in fluid communication with the line, the second fluid traveling through the line in a second direction opposite to the first direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

FIG. 1 is a schematic view of a fluid migration shut-off assembly;

FIG. 2 is a schematic view of a fluid trap of the fluid migration shut-off assembly of FIG. 1;

FIG. 3 is a schematic view of a debris catch of the fluid migration shut-off assembly of FIG. 1;

FIG. 4 is a schematic view of an alternate embodiment for a debris catch as disclosed herein;

FIG. 5 is a schematic view of an alternate embodiment for a debris catch as disclosed herein;

FIG. 6 is a schematic view of an alternate embodiment for a fluid trap as disclosed herein;

FIG. 7 is a schematic view of an alternate embodiment for a fluid trap as disclosed herein; and

FIG. 8 is a schematic view of an alternate embodiment for a debris catch and fluid trap as disclosed herein.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.

Referring now to FIG. 1, an assembly 10 is shown. The assembly 10 is included along a chemical injection line 12. The chemical injection line 12 is arranged in a borehole spanning between a surface in which the borehole is made (e.g., a surface of the Earth) and production tubing in the borehole for enabling operators at the surface to inject chemicals or the like downhole, such as demulsifiers, clarifiers, corrosion inhibitors, scale inhibitors, dewaxers, surfactants, etc., for aiding in production. The assembly 10 is arranged to prevent the migration of natural gas or other fluids, up the injection line 12 to the surface.

The assembly 10 includes a trap 14 and a debris catch 16. The chemical injection line 12 comprises several sections, namely, lines 12 a, 12 b, and 12 c. The line 12 a is connected between an inlet 18 of the debris catch 16 and the surface, the line 12 b is connected between an outlet 20 of the debris catch and an inlet 22 of the trap 14, and the line 12 c is connected between an outlet 24 of the fluid trap and the production tubing. As will be better appreciated in view of the below, the lines 12 a, 12 b, and 12 c act to reverse the direction of flow of the line 12 as it travels from the surface to the production tubing in order to trap, catch, or otherwise contain debris, gas, or other fluids undesirably located in the line 12. the injection line 12 to the surface.

Although one or more check valves are included between the production tubing and the line 12 c, it is probable that some degree of leakage, weeping, etc. will occur and that gas or other low-density fluids will escape from the production tubing and migrate up the line 12 toward the surface. For example, a difference in densities between a first fluid being injected downhole (e.g., a liquid chemical) and a second fluid flowing through the production tubing (e.g., natural gas) will result in the second fluid migrating up the line 12. That is, the more dense fluid will exert a buoyancy force on the less dense fluid equal to the weight of the more dense fluid that is displaced by the less dense fluid, causing the less dense fluid to rise and separate. The examples herein may refer to the low-density fluid as a gas, e.g., natural gas, and the high density fluid as a liquid, e.g., a liquid chemical, although it is to be appreciated that any other relatively low-density fluid could migrate up any other relatively high-density fluid or vice-versa.

An arrow 26 in FIG. 2 designates a direction of flow of the chemical fluid through the line 12. In this embodiment, a low-density fluid 28 has flowed up the line 12 c, through the outlet 24 and into the trap 14, where the low-density fluid 28 has gathered in a compartment 30 of the trap 14. The term “low-density” is used for convenience and is made with respect to the density of the injected fluid in the line 12, e.g., a chemical liquid or the like. Again, it is to be appreciated that the low-density fluid 28 has become trapped in the trap 14 because a net buoyancy force created by the difference in densities caused the low-density fluid 28 to float into the compartment 30 on top of the injected chemical fluid. The more dense fluid is free to flow along the path 26 from the inlet 22 to the outlet 24, while the low-density fluid 28 remains trapped in the compartment 30.

The inlet 22 is positioned opposite from, away from, or is otherwise secluded from the low-density fluid 28 in the compartment 30 in order to prevent the low-density fluid 28 from reaching the inlet 22 of the trap 14, where back flow, vaporization, etc. of chemical fluid may enable the low density fluid to reach the inlet 18 of the debris catch 16, and continue unobstructed up the line 12 a to the surface. In some embodiments, a plurality of assemblies 10 could be installed in series along the line 12 to further prevent migration. In another embodiment described in more detail below, a check valve is used to create a chemical fluid barrier for preventing the migration of the low-density fluid 28 further up the line 12.

A variety of methods for secluding or isolating the inlet 22 from the low-density fluid 28 is possible, although a simple embodiment is to set a vertical separation between the compartment 30 and the inlet 22. Under normal conditions, a buoyancy force has only a vertically upward component, by creating a vertical separation between the inlet 22 and the compartment 30, the low-density fluid can not escape down the line 12 b and/or up the line 12 a without first escaping the compartment 30, such as by filling its entire volume. Even if the low-density fluid 28 fills the entire volume of the compartment, as discussed in more detail below, a check valve can be incorporated to create a fluid barrier for preventing the migration of the low-density fluid up the line 12.

It is noted that debris or the like from the surface may drop down the injection line 12 and collect in the bends of the line, impeding chemical fluid flow or clogging the line 12 all together. As a result, the debris catch 16 can be utilized in some embodiments in addition to the trap 14 in order to catch debris 32 and contain the debris 32 at a containment area 34 of the debris catch 16. The chemical fluid, as again represented by the arrow 26, will not be trapped like the more dense debris, but will instead flow from the line 12 a into the line 12 b via the inlet 18 and the outlet 20 of the debris catch 16. The catch 16 thus works similarly to the trap 14, but also oppositely, in that the relatively higher density of the debris 32 causes the debris 32 to sink under the flow 26 of the fluid, instead of a relatively lower density causing the low-density fluid 28 to float atop the flow 26 of injected fluid. It should be appreciated that debris 28 could comprise solids, relatively high-density fluids (with respect to the injected fluid), or mixtures thereof. In order to prevent the back flow of chemical fluid, a check valve 36 is included at the inlet 18 of the debris catch 16. The check valve 36 could alternatively be included at the outlet 20, along the lines 12 a or 12 b, or at some other suitable location to prevent back flow. Advantageously, the check valve 36 not only prevents the back flow of injected fluid, but it also acts as yet another means for preventing the migration of low-density fluid, e.g., the low-density fluid 28, to the surface.

More than simply providing a vertical separation between the compartment 30 and the inlet 22, improved performance may be achievable by creating a vertical separation between the inlet 22 and the inlet 18, for example as shown by the line 12 b in the Figures. By arranging the inlet 22 higher than the inlet 18 and positioning the check valve 36 upstream of the trap 14, it is possible to prevent the back flow of chemical fluid, and therefore migration of low-density fluid, down the line 12 b or up out of the catch 16. That is, as the low-density fluid 28 gathers in the trap 14, any remaining chemical fluid may be forced out of the trap 14 down the line 12 c by the gathering low-density fluid. However, due to the check 36, the chemical fluid in the line 12 b will not be able to back flow, and will therefore act as a barrier for preventing the low-density fluid 28 from flowing into the catch 16 or to the surface. Alternatively stated, since the buoyancy force is directed in a vertically upward direction, the low-density fluid will not be able to flow down the line 12 b absent the back flow of chemical fluid. It is noted that the check valve 36 is subjected to virtually only the chemical fluid, and is thus much less likely to experience the same failure rates as check valves downhole that are subjected to the low-density fluids in the production tubing (e.g., hydrocarbons) and any other debris (e.g., fine sand grains) carried by the low-density fluid.

Several variations of components of the assembly 10 are shown in FIGS. 4-8. It is to be noted that some elements in FIGS. 4-8 are labeled with prime, double prime, or triple prime symbols because, while they generally resemble the corresponding elements having the same base reference numeral (i.e., those numerals without the prime symbols), at least one difference is noted herein between the elements labeled with prime, double prime, or triple prime symbols and their corresponding elements in the previously described embodiments. All other descriptions of the corresponding elements apply also to the elements identified with prime, double prime, or triple prime symbols.

In FIG. 4, a debris catch 16′ is shown (generally resembling the catch 16), having a baffle 38 and a funnel 40. The baffle 38 is included to act as a barrier for any debris, e.g., directing the debris 32 to fall into the containment area 34 of the catch 16′. The funnel 40 also acts to direct the debris into the containment area 34, where it is held. This arrangement is advantageous, for example, in the event the fluid in the catch 16′ becomes agitated, the baffle 38 and funnel 40 will act as barriers to direct the debris 32 and keep the debris from escaping. The baffle 38 or the funnel 40 could be made from a mesh or screen, for example, so that the fluid is able to flow therethrough, but the debris 32 is not. In one embodiment, the baffle 38 is formed as, or otherwise replaced by, a screen or filter spanning across the debris catch in order to isolate the outlet from the inlet of the catch. It is to be appreciated that in other embodiments the baffle 38 and the funnel 40 could be used separately.

In FIG. 5, a debris catch 16″ is shown (generally resembling the debris catch 16), having a cyclone 42 therein. An inlet 18″ is directed horizontally into the catch 16″ (as opposed to the inlet 18, which is directed vertically into the catch 16) in order to cause the fluid to circulate in the cyclone 42 for depositing the debris 32 in the containment area 34 of the catch 16″. An output 20″ may be positioned at the center of the catch 16″ to assist in the flow of fluid out of the cyclone 42. Thus, the catch 16″ provides an embodiment in which the fluid is free to flow out of the outlet of the catch while the debris is directed to and then held in the containment area.

If enough low-density fluid rises into the compartment of the fluid trap, it is possible for the low-density fluid to fill the entire volume of the compartment of the fluid trap, which could result in the low-density fluid seeping out the inlet of the fluid trap, through the debris catch, and up the line to the surface. Accordingly, it may be desirable to include a means for at least periodically removing the low-density fluid from the fluid trap. One example of an embodiment in which the low-density fluid is removable is illustrated in FIG. 6. In this embodiment, a trap 14′ is shown (generally resembling the trap 14), having a membrane 44 and a low-density fluid outlet 46 to a line 48 located in a vented compartment 30′. The membrane 44 is included in this embodiment is permeable to the low-density fluid 28, but substantially impermeable to the injected chemical fluid. This enables the low-density fluid to collect above the membrane 44 in the compartment 30′, while the chemical fluid flows normally from the line 12 b to the line 12 c. This embodiment is particularly useful if the low-density fluid is a gas and the injected chemical fluid is a liquid in that the membrane 44 may be, for example, a polytetrafluoroethylene filter or the like. In this embodiment, the low-density fluid outlet 46 is provided so that the low-density fluid 28 collected in the trap 14′ can be removed from the trap 14′. For example, the low-density fluid could be vented or pumped back down into the production tubing, into an area of the production tubing located up-hole, or to some other desired location.

As another example of a method for removing low-density fluid from the trap, the trap could be periodically flushed at an elevated fluid flow rate to force the low-density fluid back down into the production tubing. The fluid used to flush the low-density fluid could be selected such that the solubility of the low-density fluid in the injected chemical fluid is high, in order to assist in the removal of the low-density fluid from the trap. In another embodiment, a venturi pump, air aspirator, or other mechanism could be installed in, e.g., the line 48, in order to draw the low-density fluid out of the trap and pump the low-density fluid back into the production tubing or to some other desired location.

Several more aspects of the invention are appreciable in view of the embodiment of FIG. 7, namely, a trap 14″. The trap 14″ is horizontally orientated, including a horizontal inlet 22″ and a horizontal outlet 24″ (resembling the inlet 22 and outlet 24, respectively, but being horizontally oriented) and is thus installable in a horizontal section of a borehole. This embodiment still utilizes the behavior of the low-density fluid rising as a result of its relatively lower density. That is, as the low-density fluid 28 enters the outlet 24″, the low-density fluid rises into a compartment 30″ (resembling compartment 30, but partially formed by a wall 50 and being horizontally oriented), as designated by arrows 52. By partially defining the compartment 30″ with the wall 50 and placing the wall 50 sufficiently far from the outlet 24″, the low-density fluid 28 will rise into the compartment 30″ and become trapped well before the low-density fluid reaches the inlet 22″, with the wall 50 secluding or isolating the inlet 22″ from the trapped low-density fluid 28. The flow of injected fluid, as designated again by the arrow 26, will simply flow under the trapped low-density fluid 28 and out the outlet 24″.

Furthermore, in view of the trap 14″, it is to be appreciated that while a simple and effective way of secluding the trapped fluid from the inlet of the trap is to create a vertical separation between the compartment and the inlet or pathway leading to the surface (which can be further improved by the use of a check valve, as discussed above), the inlets of the trap and/or debris catch can be located at other locations as well. For example, the inlets and outlets of various embodiments could be placed in the top, bottom, side, or any other desired location of the catch or trap, so long as a compartment is formed that secludes the inlet (with respect to the direction of flow of the injected fluid) of the debris catch and/or fluid trap from the trapped low-density fluid.

FIG. 8 illustrates a combined unit 54 including both a low-density fluid trap 14′ and a debris catch 16′″ in a single, integrated assembly. In this embodiment, the line section 12 b would be unnecessary, as the trap and catch are integrated together. The illustrated embodiment of the combined unit 54 includes a baffle 60, a funnel 62 for the trap 14′, and a funnel 64 for the catch 16′″, for directing the low-density fluid 28 into the compartment 30 and the debris 32 into the containment area 34, respectively. The baffle 60 and the funnel 62 act to seclude or isolate a combined inlet 66 from the low-density fluid 28 as the low-density fluid 28 migrates up the line 12 c and enters the combined unit 54 via a combined outlet 68, while the baffle 60 and the funnel 64 act to contain the debris so it does not clog the injection line 12. The flow of fluid, as again represented by the arrows 26, flows essentially unimpeded around the baffle 60 and between the funnels 62 and 64 from the inlet 66 to the outlet 68. It is to be appreciated that that features shown could be removed, or replaced or augmented by other features, such as an outlet for venting the compartment, a permeable membrane, screens, a venturi pump, etc. Additionally, the combined unit 54 could be made rotationally symmetrical, as shown, so that it can be installed in either direction. It is also to be appreciated that, as shown in FIG. 8, the combined inlet 66 could be located lower than the combined outlet 68 and a check valve 70 could be included at the inlet 66 or in the line 12 a for creating a chemical fluid barrier, similar to the use of the check valve 36 described above, that prevents the migration of the low-density fluid 28 out of the compartment 30. That is, as the low-density fluid gathers in the unit 54, chemical fluid in the unit 54 will drain down the line 12 c, to reach the level of the outlet 68. Once the chemical fluid drops down to the level of the outlet 68, no more chemical fluid will be forced out the outlet 68 and the check valve 70 will prevent back flow out the inlet 66, thereby holding the low-density fluid 28 in the unit 54.

While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. 

1. A downhole assembly, comprising: a line operatively arranged to carry a first fluid; a trap arranged in fluid communication with the line, the trap operatively arranged to enable the first fluid to flow in a first direction, while capturing a second fluid in a compartment, thereby preventing migration of the second fluid through the line in a second direction opposite to the first direction.
 2. The assembly of claim 1, wherein a first density of the first fluid is greater than a second density of the second fluid, and the second fluid rises atop the first fluid into the compartment.
 3. The assembly of claim 2, wherein the first fluid is a liquid and the second fluid is a gas.
 4. The assembly of claim 1, further comprising, with respect to the first direction, an inlet into the trap and an outlet out from the trap, the second fluid entering the trap via the outlet, the compartment operatively arranged to seclude the inlet from the second fluid trapped in the compartment while permitting the first fluid to flow between the inlet and the outlet.
 5. The assembly of claim 1 wherein the trap includes a membrane permeable by the second fluid for isolating the compartment from the first fluid.
 6. The assembly of claim 5 further comprising a compartment outlet connected to the compartment for releasing the second fluid from the compartment.
 7. The assembly of claim 1, wherein the second fluid is natural gas.
 8. The assembly of claim 1, further comprising a catch fluidly connected to the line, the catch operatively arranged to capture debris while enabling the first fluid to flow therethrough.
 9. The assembly of claim 8, wherein the catch includes a containment area for holding the debris.
 10. The assembly of claim 9, further comprising a baffle, a wall, a funnel, a screen, a cyclone, or combinations including at least one of the foregoing for directing the debris into the containment area or the second fluid into the compartment.
 11. The assembly of claim 8, wherein the trap and the catch are integrated into a single unit having a combined inlet and a combined outlet.
 12. The assembly of claim 8, wherein the catch includes a check valve for preventing back flow of the first fluid or migration of the second fluid up the line.
 13. The assembly of claim 12, wherein the catch is located upstream of the trap with respect to the first direction.
 14. The assembly of claim 13, wherein the trap includes a first inlet and the catch includes a second inlet and the first inlet is positioned higher than the second inlet for creating a vertical separation between the first and second inlets.
 15. A method of operating a downhole system, comprising: injecting a first fluid through a line in a first direction; and capturing a second fluid in a compartment connected in fluid communication with the line, the second fluid traveling through the line in a second direction opposite to the first direction.
 16. The method of claim 15, wherein a first density of the first fluid is greater than a second density of the second fluid and the second fluid rises atop the first fluid into the compartment.
 17. The method of claim 15, further comprising pumping the second fluid out of the compartment via an outlet connected to the compartment.
 18. The method of claim 17, wherein the outlet is separated from the first fluid via a membrane, the second fluid permeable through the membrane.
 19. The method of claim 15, further comprising capturing debris traveling down the line in a debris catch, the debris catch in fluid communication with the line.
 20. The method of claim 19, wherein the debris catch is arranged at a vertically lower position than the compartment and located upstream of the compartment with respect to the first direction of flow. 